The invention relates first to a rear wheel suspension for a motor vehicle with an upper and a lower transverse control arm, a transversely arranged compensating control arm and a longitudinal control arm for multiple linking of an axle carrier to the vehicle body, with a body support consisting of a spring and a shock absorber, the lower fixing eye of the shock absorber being mounted directly on the axle carrier.
A rear wheel suspension of this kind is described in German Patent DE 34 34 790 A1. The body is here supported by means of a spring/shock absorber strut, that is, a combination of a shock absorber and a spring, the spring being supported at the bottom on the outer tube of the shock absorber. The lower fixing eye of the shock absorber is mounted on the axle carrier at the level of the wheel axis (see e.g. FIG. 2 of the application published without examination). This layout has inter alia the disadvantage that the spring/shock absorber strut protrudes very high, requiring additional packaging space which must be made available by reducing space in the wheel opening area or trunk of the vehicle.
Moreover the fixing eye is located near the pivot axis about which the axle carrier is pivoted in relation to the body during inward deflection. This causes poor transmission of force or stroke, particularly for the spring.
The invention is therefore based on the objective of providing a flat rear wheel suspension of the kind mentioned, which furthermore delivers favorable performance.
To achieve the objective it is proposed that the upper transverse control arm, referred to the direction of travel, is located in front of the lower transverse control arm and the spring is supported on the lower transverse control arm near the axle carrier. Hence the first achievement is that the bottom support of the spring is set far down, so that the top support, taking into account the spring travel which must necessarily be provided, can be arranged below the wheel opening housing or trunk floor.
By shifting the upper control arm relative to the lower control arm, secondly enough clearance space is created for the spring, so that e.g. a short barrel spring with progressive spring characteristic (miniblock spring) can be used. The arrangement further ensures that enough fitting space is left to be able to attach the caliper of a disc brake in the rear angle region of the axle carrier.
The chosen arrangement further has the advantage that the stroke path for the spring can be kept close to optimum, as the wheel contact point of the wheel held on the axle carrier and the spring support are approximately the same distance away from the pivot axis of the wheel suspension on the body.
In order to be able to arrange the upper link point of the shock absorber as low as possible and so be able to provide a load space floor continuing as far as the wheel housing, it is proposed to provide the lower link point to the axle carrier at the level of the link point for the lower cross member. At the same time the shock absorber can be arranged close to the axle carrier so that the load space, if its floor runs below the upper link point of the shock absorber, has to be only slightly restricted laterally.
For the kinematics of the wheel suspension it is advantageous if the lower transverse control arm is located behind the axis of rotation in the axle carrier and the upper transverse control arm is located more or less above the axis of rotation in the axle carrier. In this way the position of the pivot axis, which is determined inter alia by an imaginary central link of the transverse control arms on the body side, can be adapted better to the respective circumstances of the vehicle.
Preferably the shock absorber is arranged between the compensating control arm and the upper transverse control arm.
The transverse control arms and the compensating control arm are linked to an auxiliary frame on the body side. This auxiliary frame is attached to the body by four points of attachment. On one side of the vehicle, on the auxiliary frame are arranged in each case two points of attachment one behind the other and approximately halfway between the axle carrier and the link of the upper transverse control arm. The link of the compensating control arm to the auxiliary frame on the body side is approximately below the front attachment of the auxiliary frame to the body.
The arrangement of the wheel suspension on the auxiliary frame described has the advantage that the wheel suspension can be largely preassembled and attached together with the auxiliary frame to the body. A separate operation is necessary only for the link of the longitudinal control arm on the body side.
The invention further relates to an auxiliary frame for the front or rear wheel suspension of a motor vehicle, which is held on the vehicle body at at least four points of attachment, each wheel of the axle being linked to the auxiliary frame by at least one control arm, consisting of four arms which project from and are attached to a central body on each side of the vehicle in pairs and which at their free ends are attached to the vehicle body. An auxiliary frame of this kind is described in German Patent DE 39 42 794 A1. The arms are individually attached to a central body and form a cross in plan view. The free ends of the arms are attached to two longitudinal members of the vehicle body. The cross forms a reinforcement with which an increase in transverse rigidity is to be achieved. The cross prevents the two longitudinal members from being displaced laterally under load, but not from moving into a skewed position relative to each other. Torsion of the auxiliary frame about a transverse axis of the vehicle thus cannot be avoided with this arrangement, as the arms are in each case attached to each other centrally.
From German Patent DE 41 35 361 A1 is known another auxiliary frame in which the two front arms and the two rear arms each form a component which is made from two half-shells. The two double arms are joined together by two short tubes, so that an approximately rectangular frame is formed. The two tubes are passed through the hollow bodies and welded to them. This auxiliary frame is of course more torsionally rigid than the auxiliary frame according to German Patent DE 39 42 794 A1, but is more complicated to manufacture.
The invention is therefore based on the objective of developing a torsionally rigid auxiliary frame which is easy to make and also as flat as possible.
For this it is proposed that the two arms of one pair, that is, the two arms which point towards one side of the vehicle, form partial sections of a U-shaped double arm which is attached by its curved section to the central body.
In particular when the central body is a box open on both sides, with the curved section of a double arm entering the lateral openings, the result is a torsionally rigid arrangement which is also easy to manufacture. The box structure of the central body alone already ensures torsional rigidity, which is increased by the fact that the curved sections of the double arm enter the side openings and are preferably welded there.
The torsional rigidity can be increased if the box has the form of an elongate cuboid which is closed in cross-section. To facilitate assembly of the curved sections, the lateral openings are funnel-shaped.
The double arms are preferably formed from a tube which by means of a bending machine can easily be changed to the shape intended for the vehicle. A particularly good joint between the tube and the box is obtained if the height of the box corresponds to the tube thickness and the tube over the whole length of its bottom enters the opening as far as the tube axis. The upper and lower edges of the box then extend tangentially into the lateral surface of the tube, so that the two parts can be welded together without stress.
The arms are freed from control arm forces if the wheel control arms are linked directly to the central body. In particular with a double transverse control arm with upper and lower control arms, the bearing blocks for receiving the link can be arranged on the upper side and on the lower side of the central body.
It is possible to attach the bearing blocks not as component parts to the central body, but to form the bearing blocks integrally directly on the central body. Mountings for a stabilizer can also be provided on the central body.
As the construction of the auxiliary frame ensures sufficient rigidity independently of the material used, it can be made of light metal, e.g. aluminium. This has the advantage that the auxiliary frame exhibits sufficient rigidity and yet is relatively light.